This moveset works well,OverHeat will take out almost anything in it's way and it gets Stab from Arcanine's Fire Type.
ExtremeSpeed is a must and can break:Flail,Reversal,Endeavor.
Iron Tail is an option because of it's High Power,Hidden Power:Rock/Ground/Fight is also another option if you don't want IronTail.
Howl raises Arcanine's Attack power which is very useful.

Switch Arcanine when it uses OverHeat so it can regain it's Status back when send it out again into battle.
yeahhh... but Arcanine's Attack is higher than its Sp.Attack... and its Sp.movepool is extremely limited.

The physical set is better... and it also comes with Howl. :/ If the Sp.sweeping MS has Overheat, you're not gonna be able to do much damage, and it won't be able to stay in that long. :/